NO_OUT is useful when you want to hide the field on the output, but still allow users to unhide it on demand. As lots of fields from field catalog, it can be filled with ‘X’ or space (default).
If you set it to ‘X’, then as long as user will not unhide it and save it to the ALV variant, it will not be visible on the screen. But as said before it can be unhide using the display options.
Figure 68 ZDEMO_AIN_CL29 hiding of columns
In this case I’ve also filled the REPTEXT column, in order to show you that it is possible to move the columns to display. If I wouldn’t do that, then description would be empty.
Figure 69 ZDEMO_AIN_CL29 Change of the layout